A navigation system performs travel guidance for enabling a user to easily reach the selected destination. A typical example is a vehicle navigation system. The present invention is not limited to a vehicle navigation system but is applicable to other types of navigation system such as a PDA (Personal Data Assistant), a cellular phone, and other portable navigation devices. However, for the convenience of explanation, the following description is made mainly for the vehicle navigation system.
Such a navigation system detects the position of the vehicle, reads out map data pertaining to an area at the vehicle current position from a data storage medium, for example, a CD-ROM (compact disc read-only memory) or a DVD (digital versatile disc), and displays a map image on a monitor screen (display) while superimposing a mark representing the current location of the vehicle on the map image. Alternatively, such map data can be provided to the vehicle from a remote server through a communication network such as Internet.
The vehicle position is determined by a self-contained navigation sensors (e.g. a distance traveled sensor and a bearing sensor) mounted in the vehicle or by a global positioning system (GPS) including an artificial satellite (satellite navigation). The satellite enables absolute position detection and higher position accuracy than the self-contained navigation sensors. However, the satellite navigation involves problem of position detection failure such as in a tunnel or a building where the satellite radio signals are obstructed. Therefore, recent navigation systems utilize both self-contained navigation and satellite navigation to achieve improved performances.
As the present position of the vehicle changes with the travel of the vehicle, the vehicle current position mark in the map image on the screen is changed accordingly. Alternatively, the map is scrolled while the vehicle current position mark is fixed at a predetermined position, for example, at the center of the image. In either method, the navigation system enables the driver to recognize the map information of the area at the vehicle position at a glance.
When a destination is not set, such a navigation system functions as a locator map which indicates the current location of the vehicle on a map image. When the destination is set, the navigation system starts a route guidance function for setting a guided route from the starting point to the destination. Typically, the route guidance function performs an intersection guidance process in which a monitor screen displays an enlarged intersection diagram and the direction in which the vehicle is to travel while displaying the guide route on a map. When a destination is input, a CPU in the navigation system determines a most suitable guided route from the current vehicle position to the destination and successively stores nodes (expressed in longitude and latitude) constituting the guided route in a memory.
During actual traveling, the node series stored in the memory is searched for a portion of the guided route to be displayed in a map display area of the monitor screen, and the portion of the guided route is highlighted so as to be discriminable from other routes. When the vehicle is within a predetermined distance of an intersection it is approaching, an intersection guidance diagram (an enlarged or highlighted intersection diagram with an arrow indicating the direction in which the vehicle is to turn at the intersection) is displayed to inform a driver of the desired one of roads or directions selectable at the intersection.
FIG. 1A shows an example of a locator map display containing a vehicle current position mark VCP on a map image 21. Typically, a navigation system shows the street on which the vehicle is running in the map image 21 and a name of the street such as “W 190TH ST” in an information box 23 on the monitor screen. Other information such as a north pointer NP, a map scale and a current time may also be illustrated on the display screen. In this manner, the locator map display shows the current position of the vehicle on the map image, however, it does not perform the route guidance function because the destination is not set in the navigation system.
FIG. 1B shows an example of route guidance display which performs the route guidance function. The route guidance display is activated after specifying the destination. In addition to the map image 21 similar to the locator map of FIG. 1A, this example further shows an arrow indicating the direction (left) in which the vehicle is to turn at the intersection in a guidance information box 22 at the top of the screen. The guidance information box 22 also shows a name of the street “PRAIRIE AVE” which intersects with the current street “W 190TH ST” and a distance to the intersection. Thus, the navigation system indicates that the vehicle should make a left turn at the intersection with “PRAIRIE AVE”.
Typically, the current street “W 190TH ST” and the left side of the street “PRAIRIE AVE” will be highlighted in the map image 21. Further, such route guidance is accompanied by voice instructions. If the direction of travel in the next intersection is left, the navigation system gives spoken guidance such as “turn left at the next intersection”. In this example, an information box 24 at the bottom of the display screen includes information regarding the remaining distance to the final destination and an estimated time to reach the final destination.
In order to be guided by the route guidance mode such as shown in FIG. 1B, a destination must be specified in the navigation system so that the system can find one or more routes to get to the destination. FIGS. 2A-2F show examples of display shown on the monitor screen during the operation of inputting the destination.
By operating a menu key, a main menu 25 such as shown in FIG. 2A is displayed on the navigation system and a menu item “Destination” is selected from the main menu. This allows the navigation system to display a “Enter Destination by” menu 27 as shown in FIG. 2B for specifying an input method for selecting the destination. The “Enter Destination by” menu 27 lists various methods for selecting the destination including “Address” for specifying the city and address of the destination, “Intersection” for specifying the names of two streets in the city which intersect with one another, and “Point of Interest” for selecting the programmed destination based on the name, category or telephone number.
Other methods in the “Enter Destination by” menu 27 include “Recent Route” for specifying the destination based on the recent destinations saved in the navigation system, “Address Book” for selecting the address of the destination out of the addresses stored in the system, and “Map Cursor” for specifying the destination by pointing a cursor to the destination on the map. For example, the information in the address book is formed of a list of names and addresses of the places that the driver frequently visits.
When selecting, for example, the “Point of Interest” in FIG. 2B, the navigation system displays a “Category List” menu 28 such as shown in FIG. 2C. The “Category List” menu 28 contains various different categories such as 37 Bank”, “Restaurant”, “Hotel”, “Shopping” and others. Supposing the category “Shopping” is selected, the navigation system displays “Name List” such as shown in FIGS. 2D and 2E. The “Name List” shows names of shops and shopping malls sorted by, for example, distance from the vehicle. In an address information box 31 on the display, the address and phone number of the highlighted name in the list 33 will be displayed. The address information box 31 may also show the distance to the highlighted shop. Typically, the navigation system stores several tens or hundreds of names of shops within predetermined distances and displays several shops per page of display screen, and a user may scroll the display screen to see other names of shops in the name list 36 such as shown in FIG. 2E.
When the destination is not prestored in the navigation system, a user can input the destination by selecting, for example, the “Address” method or “Intersection” method in the “Enter Destination by” menu 27 of FIG. 2B. Then, the navigation system displays an “Enter Street Name” shown in FIG. 2F for inputting the city and address in an address input box 37 by means of a keyboard (keypad) 38 displayed on the monitor screen.
After inputting the destination, the navigation system determines a route to the destination based on, for example, the shortest way to reach the destination, the route preferring freeways to surface roads, or the route without using toll road, and the like. Thus, the navigation system moves to the route guidance display such as shown in FIG. 1B which performs the route guidance.
In the process of specifying the destination, there is a case where a user is familiar with his destination on a map image of a particular street although he may or may not know the address number of the street. Sometimes, a user is able to pin-point his destination on the map image even though he does not know the address number. Suppose the particular address has never been used in the system and therefore not listed in the “Address Book” or “Recent Route” (FIG. 2B) for quick reuse, the user has to specify the address of the destination through the keyboard such as shown in FIG. 2F. This input method takes time and may adversely affect the safe driving.
Therefore, in such a case, rather than hitting the keyboard one by one, for specifying the street name and address number, the user wants a quicker way to specify the destination address through the map image. For example, in many navigation systems currently in the market, a user can find a point of interest (POI) on the map image by pointing the cursor (marker) on the particular POI. Then, the navigation system displays confirmation screen which shows the street name and address number of the cursor point. This process is quicker to input the street name than that using the keyboard.
In some cases, it is easier for the user to specify the destination on the position on the map even though he does not know the address number. In other cases, a user want to go to a place based on a map image such as a park or a lake, etc., without knowing a place name or an address of the place. In the conventional navigation system, however, it is not designed to easily and quickly display the street image or easily change the location on the street image. Therefore, there is a need for a navigation system which can easily and quickly change the navigation screen to a map image of the intended street to find and specify the destination on the street.